1. Field of the Invention
The present invention relates to an apparatus for transmitting an image.
2. Related Background Art
FIG. 1 shows an image communication system using an INS net 64.
Communication adapters 2 and 4 are connected to a net 3, and color copy units 1 and 5 are respectively connected to the communication adapters. When an image scanned by the color copy unit 1 is transmitted from the communication adapter 2, data transmitted via the net 3 is received by the communication adapter 4, and is printed by the color copy unit 5.
In such a system, a desired quality of an image to be transmitted varies depending on the purpose. In some cases, high-quality images are required, but in some other cases, low-quality images can be transmitted. On the other hand, a transmission time difference due to an image quality difference corresponds to a cost difference. In this case, a user cannot clearly know whether or not required image quality is properly selected and used, and may pay an unnecessary high cost.
The relationship between the data transmission speed of the circuit of a net 64 and the cost is described below with reference to FIG. 3.
A subscriber circuit 6 of the net 64 consists of a single D channel for control and two B channels for data, and is connected to ISDN equipments A 8, B 9, and C 10 via a DSU 7.
Data transmission results in a large cost difference depending on whether one B channel is used (1B mode) or two B channels are used (2B mode). Depending on an image to be transmitted or its image quality, the 1B and 2B modes sometimes do not result in a transmission time difference. Some users assign highest priority to the transmission time by selecting the 2B channel transmission mode all the time.
As described above, in the conventional system, a user cannot clearly know whether or not required image quality is properly selected and used, and may pay an unnecessary high cost.
In order to improve quality of an image to be transmitted, the amount of image data to be transmitted increases, and the time required for transmitting the image data is undesirably prolonged.